Antibiotics Mechanisms Flashcards
The Minimal Inhibitory Concentration (MIC) defines the minimum dose needed for an antimicrobial to do what?
Be bacteriostatic
What is the most common mechanism by which antibiotics inhibit or kill bacteria?
Interference with cell wall synthesis
What is the 2nd most common mechanism by which antibiotics inhibit or kill bacteria?
Interference with protein synthesis (targets the bacterial ribosome)
What is a common mechanism by which antifungals work?
Inference with cytoplasmic (plasma) membrane function
The bacterial cell wall is synthesized by cross-linking peptidoglycan strands using what enzymes?
Penicillin Binding Proteins (PBPs)
State the mechanism of action and whether the agent is static or cidal: Penicillin
Interference with cell wall synthesis; bacteriocidal
State the mechanism of action and whether the agent is static or cidal: Cephalosporins
Interference with cell wall synthesis; bacteriocidal
State the mechanism of action and whether the agent is static or cidal: Glycopeptides / Vancomycin
Interference with cell wall synthesis; bacteriocidal
State the mechanism of action and whether the agent is static or cidal: Macrolids
Interference with protein synthesis; bacteriostatic
State the mechanism of action and whether the agent is static or cidal: Tetracyclines
Interference with protein synthesis; bacteriostatic
State the mechanism of action and whether the agent is static or cidal: Fluoroquinolones
Interference with nucleic acid synthesis; bacteriocidal
State the mechanism of action and whether the agent is static or cidal: Aminoglycosides
Interference with protein synthesis; bacteriocidal
State the mechanism of action and whether the agent is static or cidal: Sulfonamides + Trimethoprim
Interference with metabolic pathways; bacteriocidal (sulfonamides are static, but trimethoprim is cidal so together they are cidal)
What are the 4 classes of beta-lactam antibiotics?
Penicillins, cephalosporins, monobactams, carbapenems
Name 3 advantages of beta-lactams.
Non-toxic, cheap, and mostly water-soluble
Specifically, how does a beta-lactam inhibit cell wall synthesis?
It irreversibly inhibits the penicillin binding protein / transpeptidase by mimicking the D-Ala-D-Ala residues that would normally bind there
Specifically, how does a glycopeptide inhibit cell wall synthesis?
It binds to the D-Ala-D-Ala residues of a peptidoglycan strand, thus preventing the strand from cross-linking
Specifically, how does a macrolid inhibit protein synthesis?
It binds to the bacterial ribosome, blocking the exit of the growing peptide chain
Specifically, how does a tetracycline inhibit protein synthesis?
It prevents the tRNA-aa complex from attaching to the ribosome
Specifically, how does a fluoroquinolone inhibit nucleic acid synthesis?
It inhibits DNA gyrase and DNA topoisomerase
Specifically, how does an aminoglycoside inhibit protein synthesis?
It changes the shape of the bacterial ribosome so that mRNA is read incorrectly
Specifically, how do sulfamethoxazole and trimethoprim (often given together as TMP/SMX) interfere with metabolic pathways?
Sulfamethoxazole competes with PABA while trimethoprim inhibits DHF reductase, together preventing folic acid synthesis
Ampicillin, amoxicillin, and piperacillin are examples of what class of beta-lactam?
Penicillin
Cefotaxime, ceftriaxone, and cefipime are examples of what class of beta-lactam?
Cephalosporin
Compared to 1st generation cephalosporins, do 3rd generation cephalosporins have better or worse activity against Gram(+) and Gram (-) bacteria?
3rd gen has better Gram (-) activity, worse Gram (+)
Vancomycin is an example of what kind of cell wall inhibitor?
Glycopeptide
Are glycopeptides and lipoglycopeptides more effective against Gram (+) or Gram (-) bacteria?
Gram(+) - they can’t get through the porins of Gram (-) bacteria to attack their cell walls
Gentamycin, tobramycin, and amikacin are examples of what kind of protein synthesis inhibitor?
Aminoglycoside
Erythromycin and azithromycin are examples of what kind of protein synthesis inhibitor?
Macrolid
Ciprofloxacin, levofloxacin, and norfloxacin are examples of what kind of nucleic acid synthesis inhibitor?
Fluoroquinolone
